Tiny vaccine doses over time cut hay fever

KING’S COLLEGE LONDON (UK) — When a new vaccine was injected repeatedly in extremely low doses but higher in the skin, the reaction to grass pollen was reduced by 90 percent.

Researchers say the findings could lead to a hay fever vaccine that is more effective, less invasive, and less expensive for patients than those already available.

Researchers say the approach, associated with an increase in blocking antibodies in the bloodstream, defines a completely new concept in treating allergies and in the future could influence treatment of other conditions such as asthma and food allergies.

Hay fever affects one in four people in the UK. An allergic reaction to grass pollen triggers a blocked or runny nose, sneezing, itchy eyes, and in some cases asthma symptoms.  For many individuals this can interfere with work or school performance, sleep, and social activities. Tablets and sprays may temporarily relieve symptoms, but for severe cases one option is a vaccine to “switch off’” the allergy, called immunotherapy.

[sources]

The vaccines currently used involve high doses of allergen given by injection underneath the skin (subcutaneously) or sometimes as a daily tablet or drops under the tongue. In most cases this involves large numbers of injections in an allergy clinic or daily tablets/drops taken continuously, which can be inconvenient and expensive.

Published in the Journal of Allergy and Clinical Immunology, the new study shows that a series of low dose allergen injections (less than a 1000th of the usual dose) into  a higher layer of the skin (intradermally), rather than subcutaneously, led to a 90 percent reduction in skin reactivity to grass pollen.

For the study, one group of subjects received six injections of grass pollen extract at two-week intervals over 10 weeks. The participants’ allergic responses in the skin were then measured. The initial injection provoked an allergic reaction on the arm visible as a lump around 10 cm in diameter lasting 1-2 days.

Over time a dramatic 90 percent reduction was seen in the size of the lump suggesting that the allergic reaction was gradually being switched off with each injection. The size of the lump did not decrease in another group of subjects who received only two injections separated by 10 weeks. Also, during the study none of the participants reported unwanted side effects and the injections did not trigger hay fever symptoms.

The researchers believe that the method of injecting the vaccine intradermally is a major factor in its success, as the skin is a highly active immunological area—more so than underneath the skin where allergy vaccines are traditionally administered.

“The results of our study are hugely exciting. We now want to find out if this process can also switch off grass allergy in the nose and improve hay fever symptoms,” says Stephen Till, Senior Lecturer at King’s College London.  Till and colleagues have launched the PollenLITE clinical trial to further test the new approach.

Professor Stephen Durham, Head of Allergy and Clinical Immunology at Imperial College London, adds: “There is great interest in giving immunotherapy by novel alternative routes to improve uptake by the immune system. The results of this study provide an excellent foundation for going on to test the intradermal vaccine route in clinical trials.”

Source: King’s College London